This application claims priority of International application number PCT/DE00/03262, filed Sep. 14, 2000, which in turn claims priority of German application number 199 44 915.5, filed Sep. 14, 1999.
The invention relates to a drive for adjustment devices in motor vehicles, more particularly for a window lifter.
From DE OS 22 10 243 an electric drive device is known for adjusting the window in motor vehicles wherein a set of revolving gear wheels having a sun wheel and an internally toothed hollow wheel as well as several planetary wheels are coupled to an electric motor. The planetary wheels are fitted in the axial direction with two ring gears with different pitch diameters wherein the ring gears with the greater pitch diameter mesh with the sun wheel and the fixed internally toothed hollow wheel. The ring gears with the smaller pitch diameter on the other hand only mesh with the internal teeth of an output element formed as a cable drum.
From DE 40 30 489 A1 a further planetary gearing is known wherein the output element formed as the hollow wheel is driven through planetary wheels which revolve on support wheels fixed on the housing and drive the hollow wheel. The hollow wheel is provided axially on each side with circular disc-shaped guide pieces, which are guided radially along their inner circumference through rolling bearings on bearing attachments of the support wheels and support the planetary wheels against moving axially outwards.
Designs of this kind occupy a relatively large amount of structural space as a result of the axially successive arrangement of the gear elements as well as the radial overhang of the planetary wheels with the larger pitch diameter or the guide pieces over the output element. Furthermore, as a result of the central bearing on the king pin, large tilting moments occur and it is necessary to provide an expensive bearing for the output element.
From DE 44 12 898A1 a drive is known which has a motor and a toothed gearing coupled to the motor and set in a multi-part housing. In order to transfer and reduce the torque produced by the motor, the gearing has a fixed hollow wheel and a rotatable output element formed as a hollow wheel with internal teeth, in which a gearing element engages. This output element is fixedly connected to the hollow shaft which acts as the output shaft. This hollow shaft is mounted in the housing on two sections through rolling bearings wherein the rolling bearings are arranged between the external radius of the hollow shaft and the housing.
The object of the invention is to provide a drive for adjustment devices in motor vehicles that occupies little structural space, is simple to fit and enables a compact construction that can be achieved with few structural parts.
By forming a bearing device directly on at least one of the housing parts or housing halves of a divisible (multi-part) housing and supporting the output element on one such bearing area formed by the housing halves it is no longer necessary to support the output element on the motor output shaft so that this can be made shorter. Furthermore the parts required for the bearing on the shaft are omitted since the bearing for the output element, preferably a slide bearing, is produced through fitting together the housing parts. It is proposed to either coat the slide bearing regions or to provide suitable materials in order to produce an optimum sliding friction.
The bearing device is thereby preferably designed so that both axial and radial forces are absorbed and then diverted over the most direct route possible into the housing. For this the bearing device can be designed in a ring shape whereby the outer circumference of the ring-shaped bearing device corresponds to the inner circumference of the output element which is formed as a hollow wheel so that the hollow wheel need only be placed on the ring-shaped bearing device in order to produce a corresponding bearing for the output element. A bearing of this kind can be produced through a guide element projecting into the output element whereby the guide element can consist of a ring or ring sections protruding from the housing in the direction of the output element. It is likewise possible that individual guide elements, for example in the form of cylindrical pins or suitable shaped protrusions, arranged corresponding to the inner circumference of the hollow wheel of the output element, form the bearing.
As an alternative to the bearing, where guide elements project into the drive element, it is proposed that a groove be worked into the housing part or housing half in which a corresponding shaped area of the output element can engage, similar to a slide block in a slide guide.
In order to increase the degree of integration and reduce the assembly costs, it is proposed that the bearing device be formed on a part of the housing. The guide element or guide elements, already formed on the housing or the groove, are provided in the housing during its original shaping. As an alternative however, it is possible to produce the groove by subsequently fixing elements on the housing, in the same way that the guide element can be attached later, for example by adhesive, screws, welding or the like.
For technical production reasons, it is advantageous if the bearing of the output element on the housing part is formed as a slide bearing since this would save on component parts, materials and assembly costs. However, it is basically possible also to provide needle, ball or rolling bearings.
In order to achieve a compact drive which is simple to handle, it is proposed that the gearbox and motor be mounted inside the housing. Advantageously, a carrier module or door inside panel is formed as a part of the housing so that on the one hand the stability of the overall drive is increased since in this way the drive becomes an integral constituent part of the carrier module whereby expensive fixing devices can be omitted and on the other hand the production and assembly costs are reduced since overall fewer component parts are required.
A further possibility for the functional integration exists where a carrier module or door inside panel is a constituent part of the magnetic reflux, whereby a separate component part for the magnetic reflux of the motor is then unnecessary. A suitable design can be, for example where the carrier module or the door inside panel consists, at least in the region provided therefor, of a ferro-magnetic material or is coated with a material of this kind.
In a further development of the invention at least one of the housing parts has a fixed internal gear formed as a hollow wheel, whereby there is an increase in the variation for the width of the gears which can be used. Gear elements for transferring force to the output element can thereby mesh with both the internal gear of the output element and with at least one of the internal gears of the housing parts. In the case of two fixed internal gears, there is the advantage that the tilting moments which appear are taken up uniformly. The teeth of the fixed internal gears must in any case be aligned flush with each other when the force-transferring gear elements engage in the two sets of teeth. The output element in its design as an internally toothed hollow wheel is indeed also an element of the gearbox, but for reasons of clarity the output element is detailed separately.
As an alternative to an internal gear molded on the housing parts, the internal gear can also be formed by one or two separate ring gears which are made as hollow wheels whereby each ring gear is rotationally secured in the housing parts or fixed accordingly.
The gear elements, formed as gearwheels, thereby mesh with both the internal teeth of the output element and with the fixed internal teeth which are formed either in the housing parts alone or in conjunction with a separate ring gear. For this it is obviously necessary for the pitch diameter of the internal teeth of the output element to coincide substantially with the pitch diameter of the fixed internal gear. The number of teeth in the internal gear of the output element differs by at least one tooth from the number of teeth of the fixed internal gear so that when the gear elements run down on the fixed internal teeth with simultaneous engagement in the internal teeth of the output element, the output element is moved further on by the difference in the number of teeth during one complete revolution of the gear elements. In this way, a very high transmission ratio is achieved and at the same time a very compact gearbox is produced with fewer structural parts.
In order to reduce the overall weight of the gearbox, the output element which is formed as a hollow wheel can be designed ring-shaped and has the internal gear provided on the inside of the ring, preferably over the entire axial width of the inside of the ring. The outside of the ring-shaped hollow wheel is thereby preferably designed as a cable drum or as a gear wheel. The bearing of the ring-shaped hollow wheel, which advantageously has a T-shaped cross-section, is formed by a groove which is produced as the two-part housing is fitted together. Through this type of bearing, it is possible to reduce the amount of material required for the output element and to provide space for mounting the gear elements inside the hollow wheel. Furthermore, the production of the output element is facilitated and the axial structural depth is reduced.
By designing the output element as a cable drum or with external teeth, it is possible to use the gearbox in many ways. In addition to the special use as a drive for a cable window lifter, it is also possible to use this compact gearbox for arm window lifters or in other places, e.g. for seat adjustment where only a small structural space is available.
It is proposed to form the toothed gearbox in combination with a set of revolving gear wheels as a result of the high transmission ratios which can be achieved, with a Wolfrom or planetary gearbox being particularly advantageous here.
As an alternative, the toothed gearbox can also be formed in combination with a wobble gearbox, wherein to avoid the tilting movements of the bearing and to achieve dynamic balancing the wobble gearbox has two wobble wheels which are off-set by 180 degrees relative to each other. As an alternative to the wobble gearbox, it is also possible to use a harmonic-drive gearbox.
In an advantageous development of the invention, the axial extension of the gear elements is less than or equal to the maximum axial extension of the output element which has the result that the dimensions of the toothed gears are fixed substantially by the axial and radial dimensions of the output element. The maximum axial extension is thereby, as a rule, determined by the width of the cable drum or the external teeth. Furthermore, an additional protection of the gear elements is reached by mounting the gear elements inside the output element, without any extension over the output element. Furthermore, the corresponding gear housing can be kept very small and have a simple geometric shape since no projections or ledges have to be taken into consideration.
By arranging all the gear elements inside the radius of the internal gear of the hollow wheel, the maximum radial extension is determined through the external diameter of the output element which leads to a compact construction for the entire gear unit of the output element.
In another design of the invention the toothed regions of the gear elements or output element are provided with a plastic coating in order to achieve a low noise level and to ensure a smooth running of the gear wheels on each other. A plastic coating on the toothed regions furthermore has the advantage that manufacturing tolerances can be very well compensated.
In order to make the drive overall in a very compact form, the motor is preferably designed as a flat motor, wherein in particular disc rotors and flat armature motors are provided.
In an advantageous development of the invention all the components of the drive, namely the motor, the gearbox, the housing parts and the electronics unit, are configured so that during assembly they need only be supplied in one direction. Thus, for example, a housing part forms the base part which is fixed on an assembly holder and all the other component parts such as planetary support together with planetary wheels, wobble wheels, axles, armature disc and the second housing part are supplied from one and the same direction, preferably from above. This design in particular facilitates a faster assembly of the drive.
The means for supplying current to the motor are provided in the electronics unit and are contestable with the motor through openings in the housing. Thus, a mainly closed housing is produced and the external connections to the current supply of the vehicle are through the electronics unit.
Similarly, sensor elements are provided in the electronics unit and are coupled to the motor or gearbox through openings in the housing to send to the electronics unit data relating to the speed, position or power capacity of the motor. Basically it is also possible to align the sensors, e.g. optical sensors, with the gearbox in order to obtain data therefrom.